Telomere has a structure composed of DNAs and several proteins located at both ends of chromosomes of eucaryotic organisms. In the case of human, the DNA in the telomere portion (hereinafter, may be merely referred to as “telomeric DNA”) exists as approximately 10,000 base pairs which include repeating sequences of six bases, i.e., 5′-TTAGGG-3′ (SEQ ID NO: 1), and the 3′-end is overhang and forming a single strand of about 100 bases.
According to researches carried out so far, it has been known that telomeric DNAs in normal somatic cells are shortened with every cell division, and when the telomeric DNAs are shortened to approximately 5,000 base pairs, the cells reach the limit of replicative senescence and then the cells which are not capable of division are finally induced to apoptosis.
On the other hand, it has been elucidated that since the activity of telomerase that allows the shortened telomeric DNAs to elongate again is very high in 70 to 80% of cancer cells, the cells do not reach the replicative senescence and thus keep dividing. Therefore, the extension reaction of telomeric DNAs by telomerase (hereinafter, maybe merely referred to as “telomerase reaction”) has been considered as an important target in treatment of cancer in recent years, and inhibitors and inhibition methods of this reaction have been extensively investigated.
Various methods for inhibiting a telomerase reaction have been proposed, including inhibition methods by stabilization of a G-quadruplex structure. G-quadruplex structure is a quadruplex DNA structure formed with a DNA sequence that is rich in guanine bases, and the single strand portion of the telomeric DNA sequence (5′-TTAGGG-3′; SEQ ID NO: 1) is also a sequence capable of forming the G-quadruplex structure.
Since telomerase is not capable of binding to a G-quadruplex structure, the telomerase reaction can be inhibited when stable existence of the G-quadruplex structure is enabled in a telomeric DNA. In this respect, methods for inhibiting a telomerase reaction via stabilization of a G-quadruplex structure by various compounds have been proposed hitherto.
PTL 1 reports an effect of inhibiting a telomerase reaction by pyrazolone derivatives. PTL 2 reports an effect of inhibiting a telomerase reaction by compounds represented by the general formula: nitrogen-containing aromatic ring having a quaternary nitrogen atom-(NR3)p-CO-partitioning agent-(CO)m-(NR′3)q-X-an aromatic ring or a non-aromatic ring. In addition, PTL 3 reports an effect of inhibiting a telomerase reaction by compounds having structures represented by the following chemical formula 1.

NPL 1, NPL 2 and NPL 3 each report effects of inhibiting a telomerase reaction by Telomestatin, Phen-DC3 and 360A. Furthermore, NPL 4 reports an effect of inhibiting a telomerase reaction by TMPyP4. In addition, similar inhibitory effects by a perylene derivative, or quinoline and quinoline-related substances have been also reported.